Apparatus and method for checking the machining process of a machine tool

Abstract

An apparatus and a method are provided for checking a machining process of a machine tool, for example a grinding machine, to obtain information about the quantity of a material removed and the wear condition of a grinding-wheel. The apparatus comprises an acoustic sensor adapted to detect acoustic signals generated by contact between the grinding-wheel and the piece being machined, and a force-detecting sensor adapted to detect the force applied between the grinding-wheel and the piece during the machining. The method comprises processing signals provided by both sensors, defining time intervals on the basis of the signals of the acoustic sensor, and monitoring the signals of the force-detecting sensor in the time intervals.

1. An apparatus for checking the machining process of a machine tool, the machine tool including a base and a tool-carrier slide, movable with respect to the base and carrying a tool, the apparatus including:
 a support and reference system for supporting and referring a piece to be machined; 
 a first sensor, adapted for sensing the force occurring between the tool and the piece and for emitting a first output signal; 
 a second sensor, adapted for detecting the contact between the tool and the piece and for emitting a second output signal indicative of the occurrence of said contact; and 
 a processing and control unit connected to the first sensor and to the second sensor and adapted for processing said first output signal on the basis of the second output signal and for providing information on the machining process of the machine tool. 
 
   
   
     2. The apparatus according to  claim 1 , wherein said second output signal is indicative of a time interval during which there is the contact between the tool and the piece, the processing and control unit being adapted to define said time interval on the basis of the second output signal and process said first output signal at said time interval. 
   
   
     3. The apparatus according to  claim 2 , wherein said second sensor is an acoustic sensor. 
   
   
     4. The apparatus according to  claim 3 , wherein said tool is a grinding wheel coupled to said tool-carrier slide and able to rotate with respect to it, said acoustic sensor being coupled to said grinding wheel. 
   
   
     5. The apparatus according to  claim 1 , wherein said second sensor is an acoustic sensor. 
   
   
     6. The apparatus according to  claim 5 , wherein said tool is a grinding wheel coupled to said tool-carrier slide and able to rotate with respect to it, said acoustic sensor being coupled to said grinding wheel. 
   
   
     7. The apparatus according to  claim 1 , wherein said first sensor is a force-detecting sensor. 
   
   
     8. The apparatus according to  claim 7 , wherein said tool-carrier slide is coupled to a slide, movable along a transverse direction, said force-detecting sensor being connected to said tool-carrier slide and to said slide. 
   
   
     9. The apparatus according to  claim 1 , wherein said first sensor is a power-detecting sensor. 
   
   
     10. The apparatus according to  claim 1 , wherein said first sensor is a strain gauge. 
   
   
     11. The apparatus according to  claim 1 , wherein said machine tool includes a numeric control connected to said processing and control unit. 
   
   
     12. A method for checking the machining process of a machine tool, the machine tool including a base and a tool-carrier slide, movable with respect to the base and carrying a tool, by means of an apparatus, said apparatus comprising a support and reference system for supporting and referring a piece to be machined, a first sensor adapted for sensing the force occurring between the tool and the piece and for emitting a first output signal, a second sensor, adapted for detecting contact between the tool and the piece and for emitting a second output signal having a logic value indicative of the occurrence of said contact, and a processing and control unit connected to the first and to the second sensors and adapted for processing said first output signal on the basis of the second output signal, the method including the following steps:
 checking the logic value of the second output signal and detecting an instant of start, substantially corresponding to the instant at which there occurs the contact between the tool and the piece; 
 monitoring, from said instant of start, the first output signal; 
 checking the logic value of the second output signal, and detecting and instant of end, substantially corresponding to the instant at which there occurs detachment between tool and piece; 
 ending the monitoring of the first output signal at said instant of end; 
 processing said first output signal; 
 performing a comparison between the results of said processing and reference values; and 
 deciding, on the basis of the result of said comparison, the necessary operations to be carried out. 
 
   
   
     13. The method according to  claim 12 , wherein the results of the processing of the first output signal are indicative of the quantity of material removed in the course of the machining of the piece. 
   
   
     14. The method according to  claim 13 , for the checking of the machining process of a grinding machine. 
   
   
     15. The method according to  claim 12 , wherein the results of the processing of the first output signal are indicative of the sharpness condition of the tool. 
   
   
     16. The method according to  claim 15 , for the checking of the machining process of a grinding machine. 
   
   
     17. An apparatus for checking the machining process of a machine tool, the apparatus comprising:
 a support and reference system for a piece to be machined; a first sensor, adapted for sensing force between a tool of the machine tool and the piece, and for emitting a first output signal; 
 a second sensor, adapted for detecting contact between the tool and the piece, and for emitting a second output signal; and 
 a processing and control unit, in communication with the first sensor and the second sensor, and adapted for processing said first output signal on the basis of the second output signal. 
 
   
   
     18. A method for checking the machining process of a machine tool machining a piece by means of a tool, the method comprising:
 providing a first sensor for sensing force between the tool and the piece, the first sensor emitting a first output signal; 
 providing a second sensor for sensing contact between the tool and the piece, the second sensor emitting a second output signal; 
 providing a processing and control unit for receiving the first and second output signals; 
 detecting contact between the tool and the piece based on the second output signal; 
 monitoring the first output signal after detecting the contact; 
 detecting detachment between the tool and the piece based on the second output signal; 
 ending the monitoring of the first output signal after detecting the detachment; and 
 comparing results of the monitoring with reference values.